Current electrical power generation plants from thermal energy mostly use heat engines and systems, based on the closed-loop Rankine cycle, with water as a working medium. In such plants, a fuel is burnt or a nuclear reaction is performed and controlled to produce thermal energy which heats the pressurised water in a boiler, where it also undergoes a phase change and produce a high pressure and high temperature water vapour. The vaporised high pressure gaseous working medium is further superheated to higher temperature and then fed to a turbine and allowed to expand across the turbine to release thermal energy and produce mechanical work. The low pressure and low temperature spent working medium leaving the turbine is condensed in a condenser where it undergoes a phase change to form liquid water. This condensation step is necessary in the conventional heat engines facilities so that the liquid water can be economically pumped and pressurized for recycling back to the boiler to be vaporised again to complete and repeat the closed-loop thermodynamic cycle of the heat engine (Rankine Cycle).
The need for the condensation stage in conventional power generating plants results in loss of a significant portion of thermal energy of the burnt fuels, which is used to heat and vaporise the working medium and is lost to cooling agents, such as sea water or river water or air used to cool the condenser. Furthermore, conventional power generating plants use very high fuel combustion temperatures of over 1273 K (1000° C.) to vaporise the working medium under very high pressures of over 6.00 MPa and at temperatures of over 750 K (480° C.). Operating power generating plants at such a high temperature and pressure require that those power plants to be constructed robustly.
Efficiency of the power plants operating on Rankine cycle is generally low and particularly of those plants utilising lower level (temperature) energies, and is also much lower than the corresponding theoretical Carnot cycle. Although the current operating conventional power plants have been adverse factors and environmental requirements result in higher initial specific investment cost per KW power.
Prior art such as ‘Kalina Cycle’ (U.S. Pat. No. 4,489,563, dated Dec. 25, 1984) and some other patents in the field of power generation, also describe other heat engines and approaches to power generation plants from both lower and higher temperature energy sources. Those systems generally use multi-component fluids as working mediums such as ammonia-water mixtures. Although they can operate at much less harsh conditions in terms of temperature and pressure, they are characterized by relatively low thermal efficiencies as compared to the relating theoretical Carnot cycle or even Rankine cycle. This is due mainly to the unavoidable loss of significant portion of thermal energy required for operation of those power cycles to cooling agents used for cooling and condensing the Working Mediums spent vapours.
Therefore the inventor has appreciated that it is advantageous to provide a heat engine system which is capable to operate at a lower working medium vaporisation temperature (such as ammonia) than conventional power generating plants operating on Rankine Cycle which operate mainly on water as the working medium, but under similar or even higher vapour and gases pressures to the turbines. The Inventor has further appreciated that it is desirable that the heat engine is also able to operate with minimum requirement for rejection of condensation latent heat of the spent working medium to the outside environment with cooling agents or preferably that the heat engine can operate without the need for rejection of condensation latent heat of the condensing step of the conventional power cycles to the outside environment.
Embodiments of the invention seek to provide a heat engine system which can combine some of the advantageous principles and criteria to generate power, while the ultimate aim and goal of the inventor is to improve efficiency of the heat engines and produce more work and power from the energy used to operate power plants.
Embodiments of the invention can utilise various sources of thermal energy from high temperatures of over 673 K (400° C.), which are obtained from combustion of the fossil fuels, to the low level temperatures, such as that of geothermal energy of about 403 K (130° C.) and power plants waste energy (condensation) or sea water or river water of any temperature of—say over 5° C. Accordingly, embodiments of the invention may include facilities which can process the induced thermal energy and generate power and facilities which can partially or fully preserve and recycle the latent heat of condensation of the working fluid within the boundaries of the thermodynamic cycle of the proposed heat engine. The recycled heat can then supplement the induced energy to vaporise more working medium to be fed to the power turbine and generate further power and improve efficiency of the novel heat engine.